INSTRUCTIONS FOR THE USE OF THE DIASTEREOTEST FOR DETERMINATION OF THE PRESENCE OR ABSENCE OF STEREOPSIS

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B05171A000600070047-6
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 1
• Document Creation Date: December 28, 2016
• Document Release Date: April 7, 2003
• Sequence Number: 47
• Publication Date: October 17, 1967
• Content Type: REGULATION

Approved p Release 2003/05/14: CIA-RDP78B0W1A000600070047-6
Instructions for the Use of the Diastereotest
for Determination of the Presence or Absence Stereopsis
A. Let the subject examine the face of the diastereotest very briefly
at close range so that he will understand that one of the three discs protrudes
or stands out.
B. While positioned directly in front of the subject, aim the diastereotest
"between his eyes," i.e., essentially toward the bridge of the subject's nose.
The distance from the face of the diastereotest to the subject's eyes or spectacle
plane should be 5.0 + 0.5 ft. (or 1.50 + 0.15 meters).
C. Hold a large opaque card, an 8" x 10" card will do, in front of the
diastereotest and rotate the diastereotest on its axis while the face the
diastereotest is covered by the card so that the subject cannot Icnow the position
of the protruding disc.
D. Instruct the subject to watch carefully, then suddenly draw the card
away, exposing the diastereotest face to the subject for about one or two seconds
(about the length of time it takes to say "diastereotest"), and then suddenly
return it to coiner the diastereotest face. Then ask the subject, "which one of
the three spots seemed to be nearest you?" (The correct answer should be indicate"
to you by the letter on the outer t6p side of the diastereotest shield surroun,ing
the test face: B = bottom; T = top; R = right; L = left, and, of course, the
in-between values for bottom-right, top-right, etc.) Do not inform4the subject
as to whether or not he gave the correct answer, as this may enable him to detect
vicarious clues.
E. Repeat steps C and D five more times, merely noting how many of the six
times the subject fails to give the correct answer. If he gives the correct
answer every time, he ikas 4tereopsis. If he misses three or more of the six, he
does not demonstrate stereopsis. If he misses one or two out of the six, the
series of six should be repeated at least once but not more than twice. If he
gets a perfect score in one of the three series of six exposures, you can safely
assume that he demonstrated stereopsis. If none of three series of six exposures
produces a perfect score, he is not using stereopsis.
If at any time you are suspicious that the subject is utilizing some
vicarious clue to obtain correct answers, merely have him cover one eye while
you repeat the test. He should now fail the test, i.e., miss one or more out
of six trials, unless he is utilizing an unintended clue. It is possible that
the protruding disc has been shifted so that it can be identified as the one
at the most acute apex of an isosceles triangle, or it may have been damaged
to give it a detectably different surface appearance than the other two. Also
the examiner may unwittingly provide extraneous clues by his manner of questioning
his manner"of.>hdldiug the diastereotest, etc.
STAT
10/17/67
Declass Review by NIMA/DOD
Approved For Release 2003/05/14: CIA-RDP78B05171A000600070047-6